The Flat Panel Display is driven to blooming developments with evolutions of photoelectric and semiconductor technologies, and Liquid Crystal Display (referred to as LCD) among a lot of panel displays has become the mainstream on the market due to many superior characteristics like high space utilization, low energy consumption, radiation-free and low electromagnetic interference.
LCD usually includes Liquid Crystal Panel and Black Light Module (referred to as BL). Because Liquid Crystal Panel is without a characteristic of self-illumination, it is necessary to dispose BL under the Liquid Crystal Panel to provide a surface light source the Liquid Crystal Panel needs, therefore Liquid Crystal Panel can display images via the surface light source provided by the Liquid Crystal Panel.
Present BL is mainly divided into the side-light type backlight module and the direct-light type backlight module by lighting methods. In recent years, bezel slimming of the BL is required correspondingly with requirements of bezel slimming of LCD. A new model of a L-Bending printing circuit board (L-Bending PCB) is applied in the side-light type backlight module to achieve bezel slimming.
Because the L-Bending PCB is Metal Core Printed Circuit Board (referred to as MCPCB), which is more expensive to be utilized in large area and to provide a large heat-dispersing area. In present technologies, the L-Bending PCB usually connects to heat-dispersing elements to increase heat-dispersing ability. FIG. 1 is a structural schematic diagram which shows that a heat-dispersing element is utilized to connect to a L-Bending PCB. Refer to FIG. 1, the L-Bending PCB 110 comprises a plane board 111 and a vertical board 122 vertically connecting to the plane board 111. A heat-dispersing element is disposed on the plane board 111, and locked with the plane board 111 together by a screw 130. The vertical board is used to connect a light source 140, and the light source can be a light emitting diode (LED).
FIG. 2 is a sectional diagram of a straight portion along A-A line in FIG. 1. Refer to FIG. 2, the plane board comprises: a metal substrate bottom 111-a, an insulation layer 111-b, a conductive layer 111-c, and a protective layer 111-d. The insulation layer 111-b is disposed between the metal substrate bottom 111-a and the conductive layer 111-c to insulate the metal substrate bottom 111-a and the conductive layer 111-c and prevent both of them form forming shorting. The protective layer 111-d disposed on the conductive layer 111-c to confirm the conductive layer in insulating from the conductive layer 111-c. When the heat dispersing element is disposed 120 on the plane board 111, because of low heat conductivities of the insulation layer 111-b and the protective layer 111-d, the heat-dispersing-rate of the heat-dispersing element is reducing; furthermore, because of a weaker mechanical strength of the protective layer 111-d, when the heat-dispersing element 120 and the plane board 111 are locked together by utilizing a screw 120, the protective layer 111-d is damaged extremely easily to expose the conductive layer 111-c, the conductive layer 111-c and the heat dispersing element 120 are contacting together directly to form leakage, and the conductive layer 111-c is caused in shorting extremely easily as well.